Last, P.R., Naylor, G.J.P. and Manjaji-Matsumoto, B.M. 2016. A revised classification of the family Dayatidae (Chondrichthyes: Myliobatiformes) based on new morphological and molecular insights. Zootaxa 4139(3): 345-368. http://doi.org/10.11646/zootaxa.4139.3.2.

Taxonomic Notes:

Last et al. (2016) described the genus Pateobatis, consisting of five medium-size to very large, marine whiprays previously placed in Himantura (including jenkinsii).

This species has probably been misidentified as Himantura (=Pateobatis)fai in the literature (W. White, pers. obs). More specimens of both this species and of H. draco from South Africa need to be examined to resolve the taxonomic status of this species. Presently H. draco is considered a synonym of P. jenkinsii. The South African species had dark spots along the posterior margin of the disc but this form has also been reported from the Arafura Sea and off Sumatra in Indonesia. It is possible that these may in fact be colour forms of the same species. Examples of specimens with dark spots along the posterior margin of the disc, are from the Arafura Sea, Sumatra (Last and Stevens 1994, Fahmi, pers. obs. 2007), and from western Sri Lanka (Morón et al. 1998, Manjaji 2004), and Sulu Sea (B.M. Manjaji-Matsumoto, pers. obs. 2002).

Justification:
This is an amended version of the 2015 assessment to accommodate the change in genus name from Himatura to Pateobatis.

Jenkins' Whipray (Pateobatis jenkinsii) is patchily distributed in inshore waters (to 90 m depth) in the Indian and Western Central Pacific Oceans. It is taken as a utilised bycatch of tangle net, gillnet, trawl net, and dropline fisheries throughout Southeast Asia and parts of the Indian Ocean where inshore fishing pressure is intense. It is caught in particularly high numbers in the target fishery for rhynchobatids operating in the Arafura Sea. Levels of exploitation are very high throughout its range in Southeast Asia and in many parts of the Indian Ocean, hence it is under a severe level of threat within most of this range. Although no species-specific data are available, overall catches of stingrays are reported to be declining in areas of Southeast Asia for which information is available, with fishermen having to travel further and further to sustain catch levels. The species is highly sought after in Southeast Asia for the high value of its skin. Little is known of the subpopulation off southeastern Africa, although the species is probably taken as bycatch of shrimp trawlers there. Fisheries in northern Australia are generally well managed and the introduction of turtle exclusion devices (TEDs) has significantly reduced the bycatch of large stingrays. In Australia, Jenkins' Whipray is considered at minimal threat throughout its wide range as there is no information to suggest that this species has declined in this area.

This large species may have limiting life history characteristics that make it biologically susceptible to depletion in fisheries and therefore, efforts should be made to assess and monitor mortality in fisheries and population trends throughout its range. Given the continuation of high levels of exploitation throughout its range in Southeast Asia where the species is caught in multiple types of fisheries, along with evidence for declines in catches of rays, the level of decline (>30% over the last three generations) and exploitation can be inferred from overall declines in fish catches in the region, as well as from habitat loss. Jenkins' Whipray is assessed as Vulnerable globally based on inferred levels of decline and exploitation across a large part of its range, but is considered to be Least Concern in Australia.

Jenkins' Whipray has a wide but patchy occurrence in the Indo-West Pacific from southern Africa to Australia, New Guinea and north to the Philippines (Compagno and Heemstra 1984, Stehmann 1995, Manjaji 2004, Compagno et al. 2005, Last and Stevens 2009). Across northern Australia it can be found from Western Australia (Ningaloo Reef) to the eastern Gulf of Carpentaria in Queensland (Last and Stevens 2009).

Globally, shark and ray landings have declined by at least 20% since 2003, but the Indo-Pacific is amongst the regions where this decline has been more severe (Dulvy et al. 2014). Catches of sharks and rays in Southeast Asia are very high but are declining and fishers are travelling much further from port in order to increase catches (Chen 1996). Net and trawl fisheries in Indonesia (especially the Java Sea) and elsewhere are very extensive and as a result, many shark and ray species are highly exploited and stocks of most species have declined by at least an order of magnitude (Blaberet al.2009). Batoids are heavily exploited (White and Dharmadi 2007) and datasets from as early as 1963–1972 show the considerable decline in batoids in the Gulf of Thailand (Pauly 1979). Trawl and gill net fisheries are also moving further afield. For example, in Jakarta the gillnet fishery at Muara Baru travels to waters around Kalimantan due to the decline in local populations (W.T. White, unpubl. data). While species-specific data on long-term declines in elasmobranchs in the Southeast Asian region are lacking, declines of Jenkins' Whipray in Southeast Asia and elsewhere in the Indo-West Pacific are inferred given the widespread historical and continuing declines of demersal fisheries in this region (Stobutzki et al. 2006). Furthermore, the extensive loss and degradation of habitats such as coastal mangroves are another key threat to coastal and inshore species; Southeast Asia has seen an estimated 30% reduction in mangrove area since 1980 (FAO 2007, Polidoro et al. 2010).

An inshore ray, usually found at less than 50 m depth, but also reportedly to 90 m (Compagno and Heemstra 1984, Kuiter and Debelius 1994, Stehmann 1995, Manjaji 2004, White et al. 2006, Last and Stevens 2009). It is also seen in reef areas off Thailand (C. Vidthyanon, pers. comm. 2007). This species attains a maximum size of at least 150 cm disc width (DW) (~300 cm total length) (Last and Compagno 1999, White et al. 2006, Last and Stevens 2009). Males mature at about 75-85 cm DW and size at birth is around 23 cm DW (White and Dharmadi 2007, Last and Stevens 2009). Reproduction is viviparous with histotrophy (White et al. 2006). A generation length of 20 years can be estimated based on the Blackspotted Whipray (Himantura astra)(Jacobsen and Bennett 2011), but noting that the Blackspotted Whipray grows to a much smaller maximum size (80 cm disc width) than Jenkins' Whipray (150 cm DW).

Jenkins' Whipray is predominantly captured as bycatch throughout its range, but retained for its meat, highly valued skin, and cartilage in Southeast Asia and more widely in the Indian Ocean (Last and Compagno 1999, Last and Stevens 2009, Last et al. 2010).

The inshore fishing pressure for Jenkins' Whipray is high throughout much of its range in Southeast Asia. In this area, most bycatch by commercial fisheries (especially trawlers) are landed and sold as food fish. This species is captured by demersal tangle net, bottom trawl, commercial gillnet and, to a lesser extent, longline fisheries (White et al. 2006, White et al. 2010).

In Sabah (Malaysia), Papua New Guinea, and Indonesia, Himantura species are often caught and landed in the inshore fisheries (trawls and longlines) and are also taken by Danish seine fishing gear (M. Manjaji and Fahmi, pers. obs. 2007; Last et al. 2010; W. White, pers. obs. 2014). Jenkins' Whipray and other stingrays are an important retained bycatch of the commercial gillnet fishery in Indonesia that targets rhynchobatid rays in the Arafura Sea (Last and Compagno 1999; W. White, pers. obs. 2007). Catches in inshore waters have declined and these vessels are having to travel farther to sustain catches; the rhynchobatid fisheries are very intensive in this region, thus the level of exploitation is extremely high. The species has also been observed from fish market surveys within Thailand (Krajangdara 2014). Given that this species occurs in shallow, nearshore environments, ongoing and widespread degradation of coral reefs and coastal areas throughout Southeast Asia are likely contributing to declines in the region.

A prawn trawl fishery consisting of about nine vessels operates in the Gulf of Papua in southern Papua New Guinea (W. White, pers. comm. 2015). Detailed species composition data for the bycatch is not currently available, but this is currently being investigated (L. Baje, National Fisheries Authority, pers. comm. 2015), and it is possible that Jenkins' Whipray is a bycatch within this fishery.

In Australia, catch data for this species is relatively limited, though large specimens have been reported as bycatch in the Australian Northern Prawn Fishery (Stobutzki et al. 2002). However, with the introduction of turtle exclusion devices (TEDs) in the fishery, the ray bycatch has declined by 36.6% (Brewer et al. 2006) which should translate to reductions in the catch and associated mortality of Jenkins' Whipray.

There are no species-specific conservation measures in place for Jenkins' Whipray. In Australia, the use of turtle exclusion devices (TEDs) in the Northern Prawn Fishery (NPF) has been compulsory since 2000 (Day 2000) and following their introduction, ray bycatch has reduced by 36.3% (Brewer et al. 2006). It is likely to occur in some Australian marine protected areas, which would afford it refuge from fishing activities.